1. Field of the Invention
This invention relates to the field of semiconductor manufacturing, and more particularly to machines used for material transport in a vacuum handling system.
2. Description of the Related Art
Current semiconductor manufacturing equipment takes several different forms, each of which has significant drawbacks. Cluster tools, machines that arrange a group of semiconductor processing modules radially about a central robotic arm, take up a large amount of space, are relatively slow, and, by virtue of their architecture, are limited to a small number of semiconductor process modules, typically a maximum of about five or six. Linear tools, while offering much greater flexibility and the potential for greater speed than cluster tools, do not fit well with the current infrastructure of most current semiconductor fabrication facilities; moreover, linear motion of equipment components within the typical vacuum environment of semiconductor manufacturing leads to problems in current linear systems, such as unacceptable levels of particles that are generated by friction among components. Several hybrid architectures exist that use a combination of a radial process module arrangement and a linear arrangement.
One form of linear system uses a rail or track, with a moving cart that can hold an item that is handled by the manufacturing equipment. The cart may or may not hold the material on a moveable arm that is mounted to it. Among other problems with rail-type linear systems is the difficulty of including in-vacuum buffers, which may require sidewall mounting or other configurations that use more space. Also, in a rail-type system it is necessary to have a large number of cars on a rail to maintain throughput, which can be complicated, expensive and high-risk in terms of the reliability of the system and the security of the handled materials. Furthermore, in order to move the material from the cart into a process module, it may be necessary to mount one or two arms on the cart, which further complicates the system. With a rail system it is difficult to isolate sections of the vacuum system without breaking the linear motor or rail, which can be technically very complicated and expensive. The arm mounted to the cart on a rail system can have significant deflection issues if the cart is floated magnetically, since the arm creates a cantilever that is difficult to compensate for. The cart can have particle problems if it is mounted/riding with wheels on a physical rail.
A need exists for semiconductor manufacturing equipment that can overcome the inherent constraints of cluster tools while avoiding the problems of linear tools.